There remains something about the evolutionary account of our origins that sounds a little like a just-so story. Until a century and a half ago it would have been regarded by the most educated person as just that – a witty tale in slightly poor taste; science fiction perhaps, but not science. This incredulity lingers: although now firmly established in the minds of most Europeans, evolutionary theory remains highly contentious worldwide. Notoriously, this includes in the US. According to a Gallup poll conducted this year, nearly half of Americans believe we humans were created by God just as we are today, whereas a further third believe in a process of “intelligent design” guided by a divine hand. Only 15 per cent accept that we evolved unaided from some surprisingly upright apes.

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A surprising number of these mysteries concern female sexuality. The male orgasm, for example, serves a rather obvious seed-sowing function – but what is the point of its female equivalent? The popular hypothesis that such ecstasy enhances the likelihood of a subsequent pregnancy is, Barash informs us, entirely without evidence. The idea that it might motivate reluctant ladies also seems flawed: other animals don’t require an eruption of bliss in order to continue the family line. Perhaps it is simply a “non-adaptive by-product” – an incidental development to which evolution is indifferent?

Barash doesn’t think so, preferring to believe that it is more important than that. But in what way remains a riddle – and only one of many posed by the female body. Scientists cannot explain, for example, why women have prominent breasts even when they are not suckling children. Other mammals don’t. Yes, of course, men are drawn to these protruding sacks of fat – but why? No one knows, though theories abound.

As Barash points out, most books about science are accounts of what we know – threatening to give the impression that all the hard work is done. In doing the opposite and writing about the gaps in our knowledge, he hopes to inspire the next generation of Darwins and Dawkinses to take up lab coats in the pursuit of truth. The book is not a white flag in the face of the unknown but a call to arms, suffused with confidence that nature will ultimately give up all her secrets.